Increased erythrocyte sodium-lithium countertransport is observed in patients with essential hypertension. Genomic regions influencing inter-individual variation in sodium-lithium countertransport have been identified by linkage analyses. While numerous studies of complex disease traits have carried out genome-wide linkage analyses, few have successfully used this information to identify underlying disease susceptibility genes. We propose a practical research strategy to follow-up a replicated linkage peak on chromosome 10 identified from genome-wide scans for sodium-lithium countertransport. This region contains only 55 genes in the overlap of the 1 LOD confidence intervals from each Phase of the Rochester Family Heart Study. This allows for the examination of the contribution of every gene to the primary and secondary traits of interest (i.e. sodium-lithium countertransport and hypertension, respectively). The goal of the project is the identification of allelic variation influencing sodium-lithium countertransport as well as risk of developing essential hypertension.